THE LIFE CYCLE 



343 



arose the names still borne by the nauplius and zoaea 

 stages of post-embryonic development in crabs, the 

 leptocephalus stage of eels, 

 etc. We have seen that there 

 is something of a transfor- 

 mation occurring in the sala- 

 mander at the beginning of 

 its adult life, and a still 

 greater one in the frog, when 

 gills and tail are lost, new 

 mouth-parts are acquired and 

 the lungs become functional. 

 Indeed, we should not fail to 

 recognize a sort of transfor- 

 mation in ourselves during 

 our earlier years, when our 

 first set of teeth drop out 

 and we develop another and 

 larger one ; and in other 

 changes that occur later, in 

 adolescence. But the most 

 remarkable examples of meta- 

 morphosis, as well as the most 

 available for study, are found 

 among insects, and these will 

 serve us for illustration of 

 this phenomenon. 

 The transformations of insects. In all of the winged 

 insect groups there is a considerable change of form at the 

 time of entrance upon adult life. 



When these changes are least, as in the grasshopper (fig. 

 195), the wings are expanded and the reproductive organs, 

 perfected ; when they are greatest, every part of the body is 

 refashioned, and the larva bears hardly any resemblance to 



FIG. 194. Leech (Clepsine) 

 overturned, showing the brood 

 of young protected beneath the 

 body. 



